Light-weight refractory brick



R. c. PURD Y AND M. F. BEECHER. LIGHT WEIGHT REFRACTORY BRICK.

APPLICATION FILED NOV. I. I918.

Patented July R, 19%

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. To all whom it may concern:

Be it known thatwe, Ross C. Punnr and Ill Timon f Bnnorrnn, citizens ofthe United fitates of America, residing at Worcester, in t the county ofWorcester and State of Massachusetts, have invented certain new anduseful Improvements in Light-Weight Refractory Bricks, of which the"following is a full, clear, and exact specification.

Uur irivention relates to light weight refractory bricks, and moreparticularly to light wei ht refractory insulating fire bricks adaptedfor furnace linings. v

' Theordinary commercial fire brick of the 15 standard dimensions 9"xl-l-x2 t" varies in weight from 6-} to 8 pounds, averaging 7 pounds. Theweight of the fire bricks necessary to line the furnaces in a torpedoboat destroyer is such that a. decrease of one it'll to pound in weightfor each brick gives roughly four tons decrease in the total weight ofthe boat. Hence it is highly desirable that a very light weight brick beutilized, in order that the efiiciency of the fighting machine. as maybe increased by adding more armament to it, or in order that the speedof the boat may be improved. Art the same time, it is necessary'that thelighter weight brick possess large mechanical strength and extremelysohigh refractory qualities in view of the fact that the fast travelingboats require forced feed furnaces 'whose fire box linings are subjectedto intense heat conditions. Light weight refractory bricks are equallydesir as able water tube boilers where a' certain p rtion of the bricksare supported by the t hes, or as arches in locomotive fire boxes or -inother set places where the at tendent saving in weight would beadvantageous. Moreover, there is an increasing trus y for heatinsulation, and which, at samete have therefractoriness of a bio. lfirebrick.

t mpt nes sawdust with the clay and eutfthis material during the firingbur .vproxies s;- ft is equally feasible to employ itinished coal, cutstraw,'mill chaff or any otherreadily combustiblematerial'which onburning leaves no appreciable amount of specification of Letters Patent.

application tiled November 1, lots.

emand for bricks which depend upon their.

Patented July a, man.

Serial No. mores.

ash. To carry out such a process, it is necessary that the sawdust,coal, etc., be finely pulverized and carefully screened. Qnly very smallparticles should be used slnce the pores should be as small as possible.The combustible matter must also be intimately mixed with the clay by along pugging operation, otherwise the brick warps seriously. Tn view of,these diificulties, bricks as heretofore made have had a coarse cellularstructure and therefore poor insulation qualities. Moreover no lightweight No. 1 refractory fire brick has been made heretofore which couldbe considered satisfactory for the purpose above specified.

Tt is accordingly an object of our invention to improve the heatinsulating qualities of bricks and to provide a very low .weight firebrick which has high refractory quali ties and sufficient strength toadapt it for use as a furnace lining when subjected tointense heat andmechanical stress.

With this and other objects in View as will be apparent from thefollowingdisclosure, our invention resides in the composition of matterset forth herein andcovered by the appended claims.

Tn the drawings, in whichlike reference numerals indicate like parts,we-have shown one form in which a-brick may be made and its mannerofapplicationto a fire box wall;

Figure 1 illustrating a brick in perspective view; and

throughout the mass to produce the desired porosity in the brick. Forsuch a material, we preferably use atype ofclay heretofore consideredworthless by fire brick manufacturers. This clay is of the nature of.lignite and is often so called, but it is in reality a lignite claycontaining a No. l refractory clay material approximating 50% Mill llllhY of'the total mass, which when burned produces an open burning clay ashof a light bufi' color which consists mainly of a refractory clay. Therefractoriness of this ashis about that ,of cone 32. This clay in theraw state is plastic, has suflicient bond ing strength for fire bricks,and adds fine working properties to the fire brick mixture. Such anatural carbonaceous clay has extremely finely divided combustiblematter distributed throu hout its mass and more uniformly thanobtainable by mechanically mixing coal orsaw dust with clay, hence theshrinkage noticeable upon burning is well distributed throughout thebrick and to a measure dissipated, with the result that warpage isreduced to a minimum.

To produce a satisfactory porous or light weight N o. 1 refractory brickfrom a lignite clay, we may combine therewith a clay mass, comprising asingle clay or a mixture of clays, which when burned has high mechanicalstren th, is low shrinking, plastic and capable of adapting the brick towith stand expansion and contraction under heat changes and has highlyrefractory qualities. To this end, we use non-silicious clays or thosecontaining nosilica sand, since these give superior refractoriness, andpreferably a type of clay heretofore unused in this art,

6., a clay of high alumina content.

One kind of high alumina clay and the one we prefer to use contains alarge proportion of Diaspore and Gibbsite. This clay varies from 65% to75% in its content of alumina in combined forms. The water ofcombination in the clay varies from 12% to 14%. The silica contentvaries from 5% to 7%. There are also small amounts of iron and titaniumpresent, with traces 'of alkalis and alkaline earths. This clay in theraw state is hard and does not slake down readily. in water, and itsfracture has -an oolitic appearance. The essential features of such aclay are its high content of alumina and its high refractory qualities.

We find that the high alumina clay when washed in water tends to breakup into two parts of practically equal proportions, one eing a plasticmass of fine clay and the other made up of rather hard granularparticles. These granular particles tend to give a coarse texture to thebrick, whereby it may stand heat changes. If, however, the high aluminaclay is not used it is desirable to add to the mixture burned clay grog,comprising burned fire clay lumps, this grog serving as the coarseparticles which provide flexibility in the bricks permitting expansionand contraction under changes in temperature.

We may also add other refractory clays to give greater plasticity to theraw material, examples 0 these being kaolin and refractory ball clay. Itis to be noted however that the high alumina clay has the combinedqualities of the refractory, lean, high shrinking, open burning kaolin,and the refractory plastic, mechanically strong burning ball cla As aspecific example of a composition of matter involving lignite clay whichwill produce a light weight refractory fire brick of exceptionalinsulating properties the following ingredients may be used:

' Lignite clay 60% Burned clay grog 20% Kaolin 10% .Refractory ball clay10% If they are mixed in the proportions speci- 13 in accordance withknown methods, a brick of standard dimensions weighing about 3 poundswill be produced. However, such a fire brick while low in weightpossesses a porosity of about 60% and is structurally weak. For a brickof such desired qualities, it should be noted that while the mechanicalstrength of the cold brick has no bearing on its load supporting abilityat furnace tempertures in general, it is a fact that considering thisgeneral composition there is a definite relation, and a brick as lightand porous as this would fail by crushing in a standard load test athigh temperatures. By substituting high alumina. clay for the clay grog,this difficulty is overcome, the porosity is but slightly lowered andthe standard load carrying capacity and refractoriness of a No. 1 firebrick retained.

A satisfactory mixture may be compounded in the following proportions.

I Lignite clay 50% High alumina clay 30% Kaolin 10% Refractory ball clay10% ing intense heat and largestrcsses. This composition gives'a minimumweight for the necessary refractoriness and load carrying capacity ofthe best grades of No. 1 fire clay bricks and is highly superior instrength, shape and insulatin properties to one made of clay mechanicaly mixed with such combustible matter as coal, sawdust, straw, grain,chaff, etc. The refractory lignite clay and the refractory, plasticclays produce a refractory skeleton which serves to retain the shape ofthe" brick in spite of the shrinkage of the lignite clay, due to theuniformity of distribution of the carbonaceous material. As a result, asuperior, highly serviceable product is obtained for use as arefractory.

At the same time, due to the uniformity of distribution of the carbon inthe refraceas es tory lignite clay, the skeleton of the burned ble toutilize, in place of the refractory lignite clay above described, othernatural clay materials which contain sufficient carbonaceous matterintimately incorporated therein to produce the desired cellularstructure and lightness in weight. Any suitable method of manufacturewithin the knowledge and skill of those familiar with making fire bricksmay be adopted for producing these articles.

As a practical application of this type of :fire brick to marine fireboxes, reference i had to the drawings showmg a special form of brickand the manner of applying it to a furnace wall. The brick is sodesigned, as shown in Fig. 1, that it may be applied rigidly to themetal wall of the fire box or to the, ordinary brick structure of othertypes of furnace. Tn order to improve, the

All

insulating qualities of the furnace wall, we provide'this brick 1 withfeet which may be in the formof ridges or of separated pro jecting lugs2 as shown in the drawings.

The bricks are fastened to the wall 3 by All ing ceramic materials.

means of bolts 4. For this purpose, adjacent faces of bricks areprovided with cooperating semi-cylindrical channels 5 having recesses 6at their ends for holding boltheads. These bolts l, having their headslocked against the shoulders of the recesses 6, pass through suitableperforations in the furnace metal Wall and are fastened thereto by nuts7 or other suitable means.

In order to insulate the brick from the furnace wall to the greatestpossible extent, the spaces 8' between the feet 2 are filled withdiatomaceous earth, or other suitable insulation such as asbestoscement. A thin layer 9 of this material may also be placed beneath thefeet of the brick, as illustrated. Slag ging of the brick face exposedto the heat is prevented by a surface coating 10 of a re fractoryalumina cement, comprising crystalline alumina and clay or suitablevitrify- This vitrifying alumina cement fills the face pores of thebrick and serves as a protecting coating against slagging with the fuelclinker. The bricks may be set in a suitable refractory cement 11 suchas above described and the joints carefully filled to prevent access ofthe flames to the rear wall of the fire box. It is to be noted that thisbrick is preferably made the size of three ordinary bricks, therebyserving to reduce the number and the extent of the joints between bricksand the necessity for filling in these spaces with suitable cement, andtending to form a more rigid and permanent fire box structure.

By means of this composition of matter we provide a fire brick ofminimum Weight for the necessary refractory qualities and mechanicalstrength. If it is made according to the shape and dimensions describedand the firebox Wallis built as illustrated, the weight of a fire boxwall is reduced about 40% below that of walls made of the ordinary firebrick as heretofore employed. Furthermore, by utilizing thiscomposition, we produce a brick which has minute pores substantiallyuniformly distributed throughout its mass and hence has better heatinsulating qualities than heretofore obtainable in this type of brick.By varying the com position of the brick within the scope of our claimswe may provide a superior insulating brick of the ordinary type or wemay combine therewith the refractory characteristics of the fire brickand so make a brick which may serve not only to insulate against theaction of heat but to withstand a high de gree of heat and have thestandard load carrying capacity as well.

We claim 1. A composition of matter for a porous brick comprising aburned carbonaceous refractory clay mass having a high degree ofporosity.

2. A composition of matter for a porous brick comprising a burnedrefractory lignite clay mass.

3. A composition of matter for a porous brick consisting of the productresulting from burning a natural refractory clay containing combustiblematter mixed with a low shrinking, hard burning clay mass.

4. A composition of matter for alight -weight brick consisting of theproduct re- "sulting from burning a lignite clay material and a highlyrefractory clay mass.

5. A composition of matter for a light weight fire brick consisting of aburned mixture comprising a carbonaceous clay material and a lowshrinking, highly refractory clay mass having a high alumina content.

6. A composition of matter for a light weight fire brick consisting of aburned'mixture comprising lignite clay material and a highly refractoryclay containing a high content of alumina in chemical combination.

7. A composition of matter for a light weight fire brick consisting of aburned IIllX- ture comprising clay material containing combustiblematter, a highly refractory, low shrinking, non-silicious clay mass anda plastic clay.

8. A composition of matter for a light weight fire brick consisting of aburned mix ture comprising clay material containing combustible matter,a highly refractory,

non-silicious clay, a plastic clay and a clay a clay high in alumina,kaolin and refracmaterial WhlCh will give a coarse texture to tory ballclay.

the brick and adapt it to Withstand expan- Signed at Vorcester,Massachusetts, this 10 sion and contraction under heat changes. 29th dayof October, 1918.

9. A composition of matter for a light Weight fire brick consisting of aburned clay ROSS C. PURDY.

mixture comprising refractory lignite clay, MILTON F. BEECHER.

